阅读说明：本技术 一种锗太阳能电池及其制备方法和应用 (Germanium solar cell and preparation method and application thereof ) 是由 牛文龙 杨文奕 刘建庆 吴倩 于 2021-07-07 设计创作，主要内容包括：本发明公开了一种锗太阳能电池及其制备方法和应用,属于太阳能电池技术领域。本发明提供的锗太阳能电池,包括依次叠加设置的锗衬底和外延片；锗衬底远离外延片一侧表面,设置有沟槽；沟槽的设置方向与锗衬底的<111>晶向相交错。本发明的锗太阳能电池通过优化结构设计,能够实现常规刚性太阳能电池的球面弯曲,同时降低了传统锗太阳能电池的重量。(The invention discloses a germanium solar cell and a preparation method and application thereof, and belongs to the technical field of solar cells. The invention provides a germanium solar cell, which comprises a germanium substrate and an epitaxial wafer which are sequentially stacked; the surface of one side of the germanium substrate, which is far away from the epitaxial wafer, is provided with a groove; the trenches are arranged in a direction that is staggered with respect to the <111> crystal direction of the germanium substrate. According to the germanium solar cell, through the optimized structural design, the spherical bending of the conventional rigid solar cell can be realized, and meanwhile, the weight of the traditional germanium solar cell is reduced.)

1. The germanium solar cell is characterized by comprising a germanium substrate and an epitaxial wafer which are sequentially stacked;

a groove is formed in the surface of one side, away from the epitaxial wafer, of the germanium substrate;

the arrangement direction of the groove is crossed with a (111) crystal plane of the germanium substrate.

2. The germanium solar cell of claim 1, wherein the depth direction of the trench is perpendicular to the largest plane of the germanium solar cell.

3. The germanium solar cell according to claim 2, wherein the depth of the trench accounts for 70-80% of the thickness of the germanium solar cell.

4. The germanium solar cell of claim 1, wherein said epitaxial wafer comprises a middle cell and a top cell sequentially disposed from said germanium substrate.

5. The method for preparing the germanium solar cell according to any one of claims 1 to 4, comprising the following steps:

s1, growing the epitaxial wafer on the surface of the germanium substrate, and performing thermal evaporation metal increasing on the surface of one side, away from the germanium substrate, of the epitaxial wafer;

s2, sequentially carrying out first wet etching, dry etching and second wet etching on the surface of one side, far away from the epitaxial wafer, of the component obtained in the step S1 to form the groove;

and S3, carrying out back gold evaporation on the component obtained in the step S2 to obtain the germanium solar cell.

6. The preparation method according to claim 5, wherein in step S2, the first wet etching is performed for 5-7 min; preferably, after the first wet etching, the thickness of the germanium solar cell at the position where the groove is arranged is 50-60 μm; further preferably, the etching solution is a mixed system comprising hydrogen chloride, hydrogen bromide, ethanol and potassium dichromate.

7. The preparation method according to claim 5, wherein in step S2, after the dry etching is finished, the thickness of the germanium solar cell at the position where the trench is arranged is 20-35 μm.

8. The method according to claim 5, wherein in step S2, in the second wet etching, the etching solution is a hydrogen fluoride solution; preferably, after the second wet etching, the thickness of the germanium solar cell at the position where the groove is arranged is 15-20 μm.

9. A photovoltaic power supply system, characterized by comprising the germanium solar cell according to any one of claims 1 to 4.

10. A high altitude aircraft, characterized by comprising the germanium solar cell according to any one of claims 1 to 4.

Technical Field

The invention belongs to the technical field of solar cells, and particularly relates to a germanium solar cell and a preparation method and application thereof.

Background

The existing solar cells mainly comprise two types, namely flexible thin film solar cells and rigid solar cells. The flexible solar cell can be bent to a certain degree, so that the flexible solar cell is more widely applicable to scenes; however, generally, the stability and radiation resistance of flexible solar cells are poor, and the performance decay rate is high.

Therefore, the solar cell mounted on the spacecraft is generally a rigid solar cell in consideration of replacement cost of the solar cell and compatibility with the structure of the existing spacecraft.

In a rigid solar cell, the germanium triple-junction solar cell has the advantages of high conversion efficiency, high radiation-resistant threshold, small performance attenuation and the like, but the germanium solar cell also has the defects of heavy weight, incapability of realizing flexibility and the like and needs to be improved.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art described above. Therefore, the invention provides a germanium solar cell, which can realize spherical bending of a conventional rigid solar cell by optimizing the structural design and simultaneously reduce the weight of the conventional germanium solar cell.

The invention further provides a preparation method of the germanium solar cell.

The invention also provides a photovoltaic power supply system with the germanium solar cell.

The invention also provides a high-altitude aircraft with the germanium solar cell.

According to one aspect of the invention, a germanium solar cell is provided, which comprises a germanium substrate and an epitaxial wafer which are sequentially stacked;

a groove is formed in the surface of one side, away from the epitaxial wafer, of the germanium substrate;

the arrangement direction of the groove is crossed with a (111) crystal plane of the germanium substrate.

According to a preferred embodiment of the present invention, at least the following advantages are provided:

(1) the germanium solar cell provided by the invention is equivalent to thinning treatment at the groove arrangement position, so that compared with the germanium solar cell without substrate treatment, the germanium solar cell has the advantages that the weight is reduced, and meanwhile, certain flexibility is obtained, so that the germanium solar cell can be curved to a certain degree; meanwhile, because the packaging film has certain flexibility, the breakage probability is reduced in the processes of later-stage packaging and the like.

(2) The reason for the cracked surface layer of the germanium solar cell is as follows: in the preparation process of the germanium solar cell, the procedures of solution washing, throwing, ultrasonic, mechanical arm picking and placing and the like are required, so that the epitaxial wafer can be subjected to dark cracking; because the thermal expansion coefficients of each layer (an epitaxial layer, a substrate layer and the like) are different, when the germanium solar cell is subjected to high temperature of an alloy step, the internal stress of the germanium solar cell is increased, and the dark crack of an epitaxial wafer is enlarged;

the main factors for their rupture are: the germanium substrate grows along the direction crossed with the (111) crystal plane, wherein the (111) crystal plane is a cleavage plane of the germanium substrate, namely the direction which is most easy to generate dark cracks in the process or transportation composition, and the dark cracks even possibly extend to the whole germanium solar cell along the (111) crystal plane under the action of stress in the alloying step, so that the germanium solar cell is scrapped;

according to the germanium solar cell provided by the invention, on one hand, the germanium substrate is provided with a position without a groove, so that the diffusion of dark cracks can be effectively blocked, specifically, when the dark cracks meet the position without the groove, due to the existence of height difference (between the groove) and the diffusion direction of the dark cracks can be changed to be carried out along the (111) crystal face, the (111) crystal face is the slip face of the germanium crystal, the atoms are densely stacked, the chemical bonds are rich, and the (111) crystal face is easy to crack relative to the (111) crystal face;

on the other hand, the direction of the groove is arranged to avoid the (111) crystal face of the germanium substrate, namely, an induced bending direction is provided, and when the groove is bent along the induced bending direction, the tension on the (111) crystal face is smaller, which is equivalent to protecting the weakest part of the germanium substrate; meanwhile, the part of the germanium substrate which is not provided with the groove provides framework support for the whole germanium solar cell, and the strength of the germanium solar cell is considered;

therefore, compared with a germanium solar cell formed by integrally thinning the substrate, processing the germanium substrate or arranging the groove along the (111) crystal face of the germanium substrate; the germanium solar cell provided by the invention has lower fragment probability.

(3) In the germanium multi-junction solar cell, a germanium substrate serves as a bottom cell at the same time and is a rich cell with high charge accumulation and current; specifically, under the influence of the currents of the middle and top batteries, most of the current of the bottom battery is limited in the crystal, cannot be emitted and can only be converted into heat, the accumulated heat is harmful to the germanium solar battery, if the accumulated heat cannot be emitted in time, the temperature of the whole germanium solar battery is increased, the heat radiation is intensified, and the efficiency and the service life of the germanium solar battery are influenced;

the groove is formed in the germanium substrate, which is equivalent to the arrangement of the heat dissipation channel on the bottom cell, so that the heat dissipation area is increased, and the performance and the service life of the germanium solar cell are further improved; meanwhile, the groove is arranged, namely, the germanium substrate is thinned, so that the current in the bottom battery is reduced, and the heat generation is reduced.

In some preferred embodiments of the present invention, a depth direction of the trench is parallel to a (110) crystal plane of the germanium substrate.

The (110) plane is a slip plane of a germanium substrate and is a direction in which the atomic packing density is highest, and therefore, the formed chemical bonds are more dense, and the energy required for generating a dark crack (crack) is more, and thus, the generation of a dark crack is most difficult.

In some embodiments of the present invention, a depth direction of the trench is perpendicular to a maximum surface of the germanium solar cell.

In some embodiments of the invention, the depth of the trench accounts for 70% to 80% of the thickness of the germanium solar cell.

In some preferred embodiments of the present invention, the trench is provided in the germanium solar cell at a thickness of 15-20 μm.

In some preferred embodiments of the present invention, the trench is provided in a germanium solar cell with a thickness of 15 μm.

In some preferred embodiments of the present invention, the width of the trench may be adjusted according to the design curvature of the germanium solar cell.

In some embodiments of the invention, the epitaxial wafer comprises a middle cell and a top cell sequentially disposed from the germanium substrate.

In some embodiments of the invention, the mesobattery is an InGaAs mesobattery.

In some embodiments of the invention, the top cell is a GaInP top cell.

According to another aspect of the present invention, a method for manufacturing a germanium solar cell is provided, including the following steps:

s1, growing the epitaxial wafer on the surface of the germanium substrate, and performing thermal evaporation metal increasing on the surface of one side, away from the germanium substrate, of the epitaxial wafer;

s2, sequentially carrying out first wet etching, dry etching and second wet etching on the surface of one side, far away from the epitaxial wafer, of the component obtained in the step S1 to form the groove;

and S3, carrying out back gold evaporation on the component obtained in the step S2 to obtain the germanium solar cell.

The preparation method according to a preferred embodiment of the present invention has at least the following advantageous effects:

(1) the conventional dry etching has good positioning property on a position to be etched, and can effectively avoid side corrosion and morphology collapse in wet etching; however, the etching medium usually adopts plasma, and in the process, the etching medium may chemically or physicochemically react with a part to be etched to generate lattice defects or solid particles, thereby causing defects of the germanium solar cell such as electric leakage and the like;

the corrosion speed is adjustable in conventional wet corrosion; however, the side corrosion can occur due to the isotropy of the corrosion direction, the positioning performance of the position to be etched is poor, and the problem of morphology collapse can occur; meanwhile, because the direction is isotropic, the corroded part is passivated in angle and is not easy to crack;

according to the invention, the etching method of firstly performing wet etching, then performing dry etching and finally performing wet etching is adopted, so that the etching speed is increased, the etching precision is ensured, and the defects of electric leakage and the like of the germanium solar cell are avoided.

(2) Although the germanium solar cell with certain flexibility can be formed by arranging the groove on the surface of one side of the substrate, which is in contact with the epitaxial wafer, and then growing the epitaxial wafer, in order to meet the growth requirement of the epitaxial wafer, the method has high requirements on the shape of the groove and the smoothness of the substrate after the groove is formed, and meanwhile, the etching depth cannot be very deep (about 1/6 of the thickness of the substrate); in addition, the formed epitaxial wafers are distributed on the substrate in a block array;

according to the preparation method provided by the invention, the etching of the substrate is carried out after the epitaxial wafer grows, and the epitaxial wafer growth process is not required to be considered, so that the requirement on the smoothness of the surface of the etched substrate groove is lower, the etching depth of the groove can be deeper (namely the thickness of the thinned substrate is thinner), and the position of the groove on the substrate and the pattern formed by the groove are more selected; in addition, the epitaxial wafer exists in a whole wafer form, and compared with the epitaxial wafer distributed in a block shape, the effective area is higher;

in conclusion, the preparation method provided by the application has the advantages of wider process parameter range and stronger operability; and the effective area of the obtained germanium solar cell is higher.

In some embodiments of the present invention, in step S1, the epitaxial growth is performed by MOCVD (metal organic chemical vapor deposition).

In some embodiments of the present invention, step S1 further includes performing a first cleaning and a first photo-etching protection process sequentially after growing the epitaxial wafer before the thermal evaporation of the metallization.

In some embodiments of the present invention, the first cleaning, specifically, sequentially comprises acetone cleaning for 8-15min, isopropanol cleaning for 8-15min, water cleaning and spin-drying.

In some preferred embodiments of the present invention, the first cleaning, specifically, sequentially performs a cleaning with acetone for about 10min, a cleaning with isopropyl alcohol for about 10min, a cleaning with QDR (quick drain rinsing tank) and a spin-drying operation.

In some embodiments of the present invention, the first photo-etching protection is performed by using a negative photoresist, and exposing and developing with an energy of 230mj or more.

In some embodiments of the present invention, in step S1, the thermal evaporation plating metal is a positive gold electrode formed by sequentially depositing three layers of metal, namely AuGeNi, Ag and Au, on a surface of the epitaxial wafer on a side away from the germanium substrate.

In some embodiments of the invention, step S1 further includes removing the negative photoresist after the thermal evaporation of the metallization by using a blue film stripping apparatus; the specific method comprises tearing off surface metal and part of photoresist with blue film, performing ultrasonic treatment in the degumming solution for 10-20min (preferably 10min), and flushing in QDR (quick draining flushing tank).

In some embodiments of the present invention, the preparation method further includes, between step S1 and step S2, performing spin coating protection on a surface of the component obtained in step S1 on the side away from the germanium substrate, and performing surface treatment and a photoresist stripping process on a surface of the germanium substrate on the side away from the epitaxial wafer.

And carrying out surface treatment on the surface of one side of the germanium substrate, which is far away from the epitaxial wafer, so as to wash away floating substances and oxides on the surface of the germanium substrate.

In some embodiments of the present invention, step S2 further includes performing a second front side glue spreading and a second photo-etching protection before the first wet etching.

In some embodiments of the present invention, the front side spin coating uses a positive photoresist.

In some embodiments of the invention, the front surface is again homogenized, the curing temperature of the photoresist is 100-120 ℃, and the curing time is 10-20 min.

In some embodiments of the present invention, the second lithography protection is performed using a positive photoresist.

In some embodiments of the invention, the second photolithography protection is performed at a spin rate of 3000-.

In some embodiments of the present invention, the second lithography protect, the exposure energy for development is 800-.

And the second photoetching protection can be performed according to the requirements of the required germanium solar cell such as the bending degree, the developed image can be adjusted, and the image comprises the width, the number, the gap and the setting position of the groove.

In some embodiments of the invention, in the step S2, the etching time of the first wet etching is 5 to 7 min.

In some embodiments of the invention, in step S2, the first wet etching is performed to an etching depth of 60-80 μm.

In some preferred embodiments of the present invention, in step S2, the first wet etching is performed to a depth of about 70 μm.

In some embodiments of the invention, in step S2, after the first wet etching, the thickness of the germanium solar cell at the position where the trench is disposed is 50 to 60 μm.

In some embodiments of the present invention, in step S2, the first wet etching is performed by using a mixed etching solution including hydrogen chloride, hydrogen bromide, ethanol, and potassium dichromate.

In some preferred embodiments of the present invention, in step S2, the first wet etching is performed by using an etching solution in which the volume ratio of hydrogen chloride: hydrogen bromide: ethanol is 5:2: 5; the volume ratio of the mass of the potassium dichromate to the ethanol is 0.2 g/ml.

The first wet etching adopts etching solution to etch the germanium substrate at a high speed, thereby increasing the setting speed of the groove.

In some embodiments of the present invention, in step S2, the dry etching is performed by using ICP-RIE (plasma etcher).

In some embodiments of the invention, in step S2, the dry etching is performed to an etching depth of 40-60 μm.

In some embodiments of the invention, in step S2, after the dry etching is finished, the thickness of the germanium solar cell at the position where the trench is disposed is 20 to 35 μm.

In some embodiments of the invention, in step S2, after the dry etching is finished, the thickness of the germanium solar cell at the position where the trench is disposed is 20 to 30 μm.

In some embodiments of the invention, in step S2, after the dry etching is finished, the thickness of the germanium solar cell at the position where the trench is disposed is about 25 μm.

The thickness of the flexible solar cell is already approximate to the thickness of the flexible solar cell by 20-35 mu m, and the germanium solar cell has certain flexibility; but still has hidden troubles such as lattice defect, electric leakage and the like, so the second wet etching process is required to be carried out continuously.

In some embodiments of the invention, in step S2, the etching solution is a hydrogen fluoride solution.

In some embodiments of the invention, the hydrogen fluoride solution is obtained by mixing a concentrated hydrogen fluoride solution with a concentration of 49 wt% and water in a volume ratio of 1:10-1: 50; however, the concentration of the aqueous hydrogen fluoride solution may be adjusted depending on the etching effect, rate, etc.

In some embodiments of the invention, in step S2, the etching solution is BOE (english name: Buffered Oxide Etch; chinese name: Buffered Oxide etching solution; formed by mixing 49 wt% of hydrofluoric acid with water or ammonium fluoride with water).

In some embodiments of the invention, in step S2, the second wet etching is performed to a depth of about 10 μm.

In some embodiments of the invention, in step S2, the thickness of the germanium solar cell at the position where the trench is disposed after the second wet etching is 15-20 μm.

In some embodiments of the invention, in step S2, the thickness of the germanium solar cell at the position where the trench is disposed after the second wet etching is about 15 μm.

In step S2, after the second wet etching, the thickness of the germanium solar cell is thinner than that of the majority of flexible solar cells; therefore, the germanium solar cell obtained by the preparation method meets the requirements of the working conditions of the flexible solar cell.

The second wet etching has a low etching speed, and the etching speed and the etching precision are easy to control; in addition, the lattice defects and the granular impurities formed in the dry etching process can be consumed through chemical reaction in the second wet etching process, so that the electric leakage problem of the germanium solar cell is avoided.

In some embodiments of the invention, step S2 further includes performing a second cleaning process after the second wet etching.

In some embodiments of the present invention, the second cleaning comprises sequentially cleaning with acetone, replacing acetone and then cleaning again, cleaning with isopropanol and cleaning with water.

In some embodiments of the invention, the second washing is at a temperature of 38-42 ℃.

In some embodiments of the invention, in step S3, the back gold is deposited by evaporation, and the back gold material is at least one of Pd, Ag and Au.

In some embodiments of the present invention, in step S3, the back gold is evaporated, and the back gold is a Pd layer Ag and an Au layer formed in this order from a surface of the germanium substrate on a side away from the epitaxial layer.

In some embodiments of the present invention, in step S3, the back gold vapor deposition is performed by referring to a method specified by GJB (national military standard).

In some embodiments of the present invention, the preparation method further includes, after the back gold evaporation, sequentially performing steps of cap layer etching, ARC (english name: anti-reflection coating; chinese name: anti-reflection coating) evaporation, alloy, ARC alignment, third photoresist protection (front side photoresist leveling), cutting, passivation, photoresist stripping, testing, and the like.

According to a further aspect of the present invention, a photovoltaic power supply system including the germanium solar cell is provided.

According to a further aspect of the present invention, there is provided a high altitude aircraft comprising the germanium solar cell.

The high-altitude aircraft according to the preferred embodiment of the invention has at least the following beneficial effects:

the germanium solar cell provided by the invention can be attached to the surface of the high-altitude aircraft due to the fact that spherical bending can be realized, so that the gas resistance in the flight process is reduced, the oil consumption of the high-altitude aircraft is further reduced, and the cruising ability of the high-altitude aircraft is improved.

Drawings

The invention is further described with reference to the following figures and examples, in which:

fig. 1 is a schematic structural diagram of a germanium solar cell obtained in embodiment 1 of the present invention;

FIG. 2 is a schematic structural view of a part obtained in step D9 according to example 1 of the present invention;

FIG. 3 is a schematic structural view of a part obtained in step D10 according to example 1 of the present invention;

FIG. 4 is a schematic structural view of a part obtained in step D11 according to example 1 of the present invention;

FIG. 5 is a schematic structural diagram of a part obtained in step D12 in example 1 of the present invention.

Reference numerals:

100. photoresist;

200. a germanium substrate, 210, a groove, 211, a first-stage groove, 212 and a second-stage groove; 220. non-etched region 221, first-stage non-etched region 222, second-stage non-etched region

300. An epitaxial layer.

Detailed Description

The concept and technical effects of the present invention will be clearly and completely described below in conjunction with the embodiments to fully understand the objects, features and effects of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and those skilled in the art can obtain other embodiments without inventive effort based on the embodiments of the present invention, and all embodiments are within the protection scope of the present invention.

Example 1

The embodiment prepares the germanium solar cell, and the specific process is as follows:

D1. growing a middle cell and a top cell of the solar cell epitaxial wafer 300 on the surface of the germanium substrate 200 by using an MOCVD method;

D2. cleaning the part obtained in the step D1, specifically, sequentially cleaning with acetone for 10min, cleaning with isopropanol for 10min, washing with water, and spin-drying;

D3. performing photoetching protection on the part obtained in the step D2, specifically adopting a negative photoresist, wherein the developing exposure energy is 230 mj;

D4. and (3) carrying out thermal evaporation metal increment on the component obtained from the component D3, wherein the adopted instrument is an atomic beam evaporation coating machine, and the positive gold specifically comprises the following components: an AuGeNi layer, an Au layer, an Ag layer and an Au layer are sequentially formed along the epitaxial layer 300 far away from the surface of the germanium substrate 200;

D5. removing the photoresist arranged in the step D3 by using a blue film stripping machine, wherein the specific photoresist removing process comprises the steps of performing ultrasonic treatment on the part obtained in the step D4 in a photoresist removing liquid for 10min, and flushing in a QDR (quick draining flushing tank);

D6. performing glue spreading protection treatment on the part obtained in the step D5 on one surface far away from the Ge substrate again (see step D3 for a specific method);

D7. carrying out back etching and photoresist stripping treatment on the part obtained in the step D6 (see step D5 for a specific method);

D8. d7, carrying out front protection spin coating on the part obtained in the step D7, wherein the photoresist is a positive photoresist, the spin coating speed is 2000r/s, the photoresist is baked for 20min by using an oven after being spin coated, and the baking temperature is 100 ℃, so that the photoresist is cured;

D9. d8, performing spin coating 100 on the surface of the part obtained in the step D8, wherein the Ge substrate is exposed, the type of the photoresist is AZ-4620, the spin coating speed is 3500r/s, the part is baked in an oven after spin coating, the temperature of the oven is 100 ℃, the baking time is 10min, and the developing exposure energy is 800 mj;

D10. etching the germanium substrate 200 of the component obtained in the step D9 by a wet etching method to an etching depth of about 70um to form a first-stage groove 211 and a first-stage unetched region 221; wherein the corrosion liquid comprises the following components in percentage by weight: hydrogen bromide: ethanol: the volume ratio of the potassium dichromate is approximately equal to 5:2:5: 1;

D11. dry etching the germanium substrate of the component obtained in the step D10 by adopting an ICP-RIE method, wherein the etching position is the position of wet etching in the step D10, and the etching depth is about 50 um; forming a second-stage trench 212 and a second-stage unetched region 222;

D12. wet etching the germanium substrate of the component obtained in the step D11, wherein the etching position is the position of dry etching in the step D11, and the etching depth of the etching solution BOE is about 10 um; forming a trench 210 and an unetched region 220;

D13. performing photoresist removing treatment on the part obtained in the step D12, specifically sequentially treating the part with acetone for 10min, changing the acetone, treating the part again for 10min, treating the part with isopropanol for 10min, and finally performing flushing treatment;

D14. d13, carrying out back gold evaporation plating treatment on the component obtained in the step D13, wherein the back gold is a Pd layer, an Ag layer and an Au layer which are sequentially superposed along the surface of the germanium substrate, which is far away from the epitaxial wafer;

D15. sequentially carrying out cap layer corrosion and ARC evaporation on the component obtained in the step D14;

D16. and (4) carrying out one-time photoetching on the part obtained in the step (15) for aligning the main gate metal which leaks out of one surface far away from the Ge substrate, so that the rear end of the part is convenient to carry out a welding process.

D17. The part obtained in the step D16 is subjected to alloy treatment, and the surface is subjected to a cutting process, so that the part can be cut according to the cutting paths reserved in the step D2.

In the germanium substrate used in this embodiment, the growth direction of the epitaxial wafer 300 (i.e., the direction perpendicular to the maximum surface of the germanium substrate) is a direction in which the (110) plane is shifted by 9 ° to the (111) plane, and thus the direction perpendicular to the maximum surface of the germanium substrate is away from the direction of the cleavage plane (111).

The schematic structural diagram of the bottom view of the germanium solar cell obtained in this embodiment is shown in fig. 1;

the structural schematic diagrams of the front views of the parts obtained in the steps D9-D12 of this embodiment are shown in FIGS. 2-5.

The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the gist of the present invention. Furthermore, the embodiments of the present invention and the features of the embodiments may be combined with each other without conflict.